The present invention relates to a method of restoring semiconductor device performance, and more particularly to a method of removing contaminant metal residue from an organic passivation layer overlying a semiconductor device.
Semiconductor devices utilizing voltages in excess of about 100 volts are frequently provided with an organic passivation layer overlying various protective layers and electrodes thereof. Further manufacturing steps, such as that of connecting a solder "bump" to an electrode of such a semiconductor device, involve depositing different layers of metal onto an entire surface of the semiconductor device. Such entire surface comprises desired locations for such metal layers as well as the passivation layer on which the metal layers are not desired. It is known that the metal layers on the passivation layer serve as "contaminant" metal layers which should be removed. Accordingly, a procedure has been used which is aimed at removing such contaminant metal layers. This procedure comprises subjecting the contaminant metal layers to a wet chemical etchant which is acidic or alkaline. Such wet chemical etchant procedure frequently leaves contaminant metal residue from the contaminant metal layers on the passivation layer. Such contaminant metal residue has been found to be responsible for seriously degrading the performance of the semiconductor device.
There are several reasons why the wet chemical etchant procedure may leave contaminant metal residue on the passivation layer of a semiconductor device. First, this procedure involves many parameters which are difficult to reproduce accurately. Consequently, only sporadic success in removing the contaminant metal layers has been attained. Secondly, because the semiconductor device is immersed in a bath of liquid etchant during this procedure, metal which has been removed from the contaminant metal layers can travel in the liquid etchant and reattach to the passivation layer to contribute to contaminant metal residue. Additionally, a drawback of using a wet chemical etchant if it is used too forcefully in attempting to fully remove the contaminant metal layers (for example, by using an overly-strong chemical etchant, or by using a chemical etchant for an overly-extended period of time), poses risks of damage to the semiconductor device. These risks include severe etching or "attack" of exposed metal portions of the device and liftoff of the passivation layer. It would be desirable to provide a method of removing contaminant metal residue from a passivation layer of a semiconductor device which is reliably successful. It would also be desirable to provide a method for removing contaminant metal residue from a passivation layer of a semiconductor device which is not destructive of the semiconductor device.